55 Orionis (HIP 27658)

55 Orionis is a blue-white main-sequence star in the constellation Orion. At 1,032 light years away, it shines at an apparent visual magnitude of 5.34. It is moving through the Galaxy at a speed of 12.6 km/s relative to the Sun.

Sky position: RA 5h 51.4m, Dec -7° 31.1'

Common designations: 55 Orionis, HR 2031, HD 39291, HIP 27658, Gaia DR3 3018839092527305856

55 Orionis has the spectral type B2V. B-type stars are hot (about 10,000 to 30,000 K), luminous and blue-white. They are massive, short-lived stars, typically only tens of millions of years old, and are common in young clusters and OB associations. Its luminosity class V means it is a main-sequence (dwarf) star, still fusing hydrogen into helium in its core like the Sun.

How to find 55 Orionis in the sky

55 Orionis lies in Orion. With a declination of -7° 31.1', it is visible from the entire Southern Hemisphere and from the Northern Hemisphere up to about latitude 82° N. It is bright enough to see with the naked eye under dark skies. It is highest in the sky at local midnight around January, which makes the weeks around that month the best time to observe it.

Tabulated data for 55 Orionis

Astrometry and spectroscopy

Right Ascension (J2000)	87.84159848° (5h 51.4m)
Declination (J2000)	-7.51800303° (-7° 31.1')
Galactic Longitude	212.89033602°
Galactic Latitude	-16.75570333°
Proper motion RA	0.04 mas/yr
Proper motion Dec	-0.66 mas/yr
Parallax	3.16 ± 0.13 mas
Spectral Type	B2V
Radial Velocity	12.60 km/s

Photometry

Band	Magnitude	Abs. Mag.
U	4.32	-3.18
B	5.15	-2.35
V	5.34	-2.16
J	5.78	-1.72
H	5.86	-1.65
K	5.91	-1.59

Colour index B-V: -0.19

Derivations

Heliocentric distance: 316.41 pc (1,032 light years) (4.2% margin of error)
Absolute visual magnitude: -2.16
Transverse velocity: 1.0 km/s
Space velocity relative to the Sun: 12.6 km/s
Galactic position (X, Y, Z): -254.4 pc, -164.5 pc, -91.2 pc
Galactic velocity (U, V, W): -9.5 km/s, -7.3 km/s, -4.0 km/s

Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.